Method and apparatus for separating semiconductor devices from a wafer

ABSTRACT

An embodiment method for separating semiconductor devices from a wafer comprises using a carrier which acts an adjustable adhesive force upon the semiconductor devices and removing the semiconductor devices from the carrier by applying a mechanical or acoustical impulse to the carrier.

BACKGROUND

Semiconductor devices are fabricated from thin wafer layers. During thefabrication process, for example during separation of the wafer intoindividual semiconductor devices, the wafer may be attached to acarrier. For subsequent processing it may be necessary to separate thesemiconductor devices from the carrier and to place them in a package orany other kind of transportable entity.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of embodiments and are incorporated in and constitute apart of this specification. The drawings illustrate embodiments andtogether with the description serve to explain principles ofembodiments. Other embodiments and many of the intended advantages ofembodiments will be readily appreciated as they become better understoodby reference to the following detailed description. The elements of thedrawings are not necessarily to scale relative to each other. Likereference numerals designate corresponding similar parts.

FIG. 1, which includes FIGS. 1A-1I, depicts various stages of a processof separating semiconductor devices from a wafer.

FIG. 2 depicts a flow diagram of an embodiment of a process forseparating semiconductor devices from a carrier and transferring thesemiconductor devices to another carrier.

FIG. 3 depicts an embodiment of an apparatus for separatingsemiconductor devices from a carrier.

DETAILED DESCRIPTION

The aspects and embodiments are now described with reference to thedrawings. In the following description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of one or more aspects of the embodiments. It is to beunderstood that other embodiments may be utilized and structural orlogical changes may be made without departing from the scope of thedescribed embodiments. It should be noted further that the drawings arenot to scale or not necessarily to scale.

In the following detailed description, reference is made to theaccompanying drawings, which form a part thereof, and in which specificembodiments are shown by way of illustration. It may be evident,however, to one skilled in the art that one or more aspects of theembodiments may be practiced with a lesser degree of the specificdetails. In other instances, known structures and elements are shown inschematic form in order to facilitate describing one or more aspects ofthe embodiments. In this regard, directional terminology, such as “top”,“bottom”, “left”, “right”, “upper”, “lower” etc., is used with referenceto the orientation of the Figures being described. Because components ofembodiments can be positioned in a number of different orientations, thedirectional terminology is used for purposes of illustration and is inno way limiting. It is to be understood that other embodiments may beutilized and structural or logical changes may be made without departingfrom the scope of the present disclosure. The following detaileddescription, therefore, is not to be taken in a limiting sense, and thescope is defined by the appended claims.

The semiconductor devices described further below may be of differenttypes, may be manufactured by different technologies and may include forexample integrated electrical, electro-optical or electro-mechanicalcircuits and/or passives, logic integrated circuits, control circuits,microprocessors, memory devices, etc.

The semiconductor devices can be manufactured from any semiconductormaterial like, for example Si, SiC, SiGe, GaAs, and, furthermore, maycontain inorganic and/or organic materials that are not semiconductors,such as for example insulators, plastics or metals.

In the following a method for separating semiconductor devices from awafer will be described using FIGS. 1 and 2.

During fabrication of semiconductor devices the semiconductor devicesmay be formed within a semiconductor wafer. The semiconductor devicescomprise an active side which may comprise a single device such as atransistor according to an embodiment or an integrated circuit accordingto an embodiment. According to an embodiment a protective layer may bedeposited onto the semiconductor devices. The protective layer mayprotect the individual semiconductor devices from environmental harms,for example during further handling of the semiconductor devices.

Wafers can be diced to fabricate individual semiconductor devices.According to an embodiment dicing is performed by sawing the wafer alongpredefined sawing streets. According to an embodiment sawing isperformed using a mechanical saw. According to an embodiment dicing isperformed by etching or by a combination of etching and sawing.According to an embodiment the semiconductor devices are not separatedcompletely in the dicing step. That is, the semiconductor devices arestill connected to a continuous part of the wafer that was not sawed oretched in the dicing step. The continuous part of the wafer is on theside opposite of the active side of the semiconductor devices.

The semiconductor devices may be subjected to a test of certaincriteria. According to an embodiment testing is performed before thewafer is placed onto a carrier. Some semiconductor devices may not meetthe test criteria and may be labeled as rejects for subsequentprocessing. Usually only a small fraction of the semiconductor deviceson a wafer does not meet the test criteria.

Referring now to FIG. 1, various stages of a process of separatingsemiconductor devices from a carrier are shown. Note that FIGS. 1A-1Idepict a cross sectional view of the stages of the process.

FIG. 1A depicts a wafer comprising semiconductor devices that may havebeen fabricated as described above. The semiconductor devices 1 may bearranged on the wafer 2 with a first side 2A, which may be called thefront side of the wafer and a second side 2B, which may be called theback side. The active side 11 of the semiconductor devices may be theone on the front side. The semiconductor devices may be subjected to atest of certain criteria as mentioned above. The semiconductor devicesthat do not meet these criteria are labeled as rejects 12.

Furthermore, the wafer may comprise predetermined semiconductor devices13 which have different dimensions than the majority of semiconductordevices 1 and may serve a different purpose. For example, in oneembodiment the predetermined semiconductor devices 13 may be larger thanthe majority of the semiconductor devices 1.

Referring to FIG. 1B, a grinding tape 3 may be laminated onto the frontside of the wafer. In other embodiments other suitable carriers may beused to fixate the wafer. The semiconductor devices may be singulated bygrinding the back side 2B of the wafer to a plane 2C. Thus theindividual semiconductor devices are physically separated. Aftergrinding a wafer edge ring 21 may remain.

Referring to FIG. 1C, an adhesive foil may be laminated onto the newback side 2C of the wafer. The adhesive foil may be connected to astructural support to improve the stability of the adhesive foil. Inother embodiments another suitable carrier may be used instead of theadhesive foil. In a next step the grinding tape may be removed from thefront side of the wafer.

As shown in FIG. 1D, the wafer edge ring 21 may be removed from theadhesive foil.

As depicted in FIG. 1E, rejects 12 may be removed from the adhesivefoil. Removal of rejects may, for example, be performed by nullifyingthe adhesion between the rejects and the adhesive foil using a laser. Inanother embodiment the rejects may be removed by mechanical picking 120.

In some embodiments the adhesive force between the adhesive foil and thewafer may be reduced by applying some outside influence to the adhesivefoil. For example, in one embodiment the adhesive foil is a UV curabledicing tape and the adhesive force can be reduced by irradiating the UVcurable dicing tape with UV light.

Referring to FIG. 1F, a carrier 4 may be attached to the front side ofthe semiconductor devices in one embodiment. In another embodiment acarrier may be attached to the back side of the semiconductor devicesafter laminating adhesive foil to the front side of the semiconductordevices and removing the adhesive foil from the back side in anadditional lamination and delamination step. In yet another embodimentthe carrier 4 instead of the adhesive foil shown in FIG. 1C may beattached to the back side 2C of the semiconductor devices.

An adhesive force of the carrier 4 can be adjusted by exposing thecarrier to a certain condition depending on the specific type of thecarrier.

The carrier may be a thermo-release foil in one embodiment and may be aanother suitable carrier in other embodiments.

UV curable dicing tapes can be used as carriers for semiconductordevices. An adhesive force of UV curable dicing tapes can be decreasedby applying UV light to them. However, some non-zero adhesive force mayremain after applying UV light.

An adhesive force of the thermo-release foil may be adjusted by applyingheat to the thermo-release foil. For example, the adhesive force may bereduced to a value significantly lower than possible in UV curabledicing tapes or close to zero.

According to an embodiment the thermo-release foil is heated to asuitable temperature and for a suitable period of time to reduce theadhesive force of the foil. In particular the thermo-release foil may beheated to 120° C. for two minutes.

Applying heat can for example be done by using a hot plate. According toanother embodiment heating can be performed using an infrared lamp.According to yet another embodiment heating can be performed using anoven or a hot air dryer. According to an embodiment heat is applied tothe side of the carrier 4 that does not bear semiconductor devices.

Referring to FIG. 1G, a mechanical or acoustical impulse 5 may beapplied to the carrier 4. According to an embodiment the mechanical oracoustical impulse is applied after applying heat to the thermo-releasefoil. According to an embodiment the mechanical or acoustical impulse isapplied to the side of the carrier 4 that does not bear semiconductordevices.

According to an embodiment the mechanical or acoustical impulse isgenerated by directing one or more gas streams at the carrier 4. The gascan be air or another suitable gas like, for example, nitrogen or argon.According to an embodiment the gas is emitted in one or more pneumaticpulses. The pulses can be, for example, 0.5 to 5 seconds, in particularabout 2 seconds long. According to an embodiment the gas jet or gas jetsmay be directed at the side of the carrier that does not bearsemiconductor devices.

The mechanical or acoustical impulse may cause vibrations in the carrier4. Due to these vibrations some or all of the semiconductor devices maydetach from the carrier after applying the mechanical or acousticalimpulse. According to an embodiment all or close to all devices detach.

The pulsing application of the gas jets generates less acceleration thana continuous application and minimizes the risk of damaging thesemiconductor devices separated from the carrier by them striking anysurface.

According to an embodiment an acoustical impulse instead of a mechanicalimpulse may be used to detach the semiconductor devices from thecarrier. The acoustical impulse can, for example, be generated using asound output system.

Advantageously, by using gas jets to create the impulse no mechanicalinteraction with the thermo-release foil is necessary, which mightdamage the thermo-release foil.

Referring now to FIG. 1H, semiconductor devices detached from thecarrier 4 may be transferred to a mechanical separating unit 6. Themechanical separating unit 6 is configured to isolate the predeterminedsemiconductor devices 13 from the semiconductor devices 1. In particularthe mechanical separating unit 6 may be a sieve sporting openings withdimensions such that semiconductor devices 1 can pass through andpredetermined semiconductor devices 13 can not.

Referring now to FIG. 1I, the semiconductor devices 1 may be transferredto an apparatus 7 which is configured to sort and align thesemiconductor devices. According to an embodiment the apparatus is abowl feeder and the semiconductor devices are aligned on a tape 8.

FIG. 2 depicts a flow diagram of a preferred embodiment of the methodfor separating semiconductor devices from a carrier described above. Themethod 200 comprises relaminating a wafer onto a thermo-release foil(201), detachment of the semiconductor devices from the thermo-releasefoil by applying heat and gas jets (202), mechanical separating of thesemiconductor devices 203, and sorting and aligning of the semiconductordevices (204).

Advantageously, the method for separating semiconductor devices from acarrier described above is a fast, gentle and cheap process which mayhelp to reduce costs in the fabrication of semiconductor devices. Due tothe method being a parallel process (concurrent release of most or allsemiconductor devices), it is faster than serial picking and placingprocesses. The described method produces no residues of any media and isenvironment-friendly and non-toxic.

FIG. 3 depicts a cross sectional view of an embodiment of an apparatusfor separating semiconductor devices from a carrier.

The apparatus 300 comprises a bearing 301. The bearing comprises acarrier retainer 301A configured to receive a carrier 4 withsemiconductor devices 1 attached to the carrier 4. The carrier 4 may bea thermo-release foil. The bearing 301 further comprises a fixture 301Bconfigured to receive a module 302. The carrier retainer 301A and thefixture 301B are configured such that the module 302 is in closeproximity to or touches the side of the carrier 4 where no semiconductordevices are attached.

The module 302 comprises a heating element 302A configured to heat thecarrier 4. The module 302 further comprises one or more gas nozzles 302Bconfigured to direct one or more gas jets at the carrier 4.

The heating element 302A may, for example, heat the carrier 4 to asuitable temperature for a suitable period of time to facilitate releaseof the semiconductor devices from the carrier 4. The gas nozzles may,for example, direct one or more gas pulses of about 2 seconds durationat the carrier.

In another embodiment the module 302 may comprise a sound output systemconfigured to apply an acoustical impulse to the carrier 4 instead ofgas nozzles.

The apparatus 300 further comprises a mechanical separating unit 6configured such that semiconductor devices separated from the carrier byapplying heat and air jets to the carrier fall onto the mechanicalseparating unit.

After passing the mechanical separating unit 6 the semiconductor devicesfall into a cone 303 configured to transfer the semiconductor devicesinto a reservoir 305. According to an embodiment the reservoir is atransport container. According to an embodiment the semiconductordevices may be transferred directly into a bowl feeder instead of atransport container.

The apparatus further comprises a vibration unit 304 which is configuredto vibrate the mechanical separating unit 6 and the cone 303. Vibratingmay help to mechanically separate the semiconductor devices and totransfer them to the transport container.

The individual components of the apparatus, specifically the module 302,the mechanical separating unit 6, the cone 303 and the vibration unit304 are configured such that the semiconductor devices are not damagedby excessive heat or excessive mechanical force. The dimensions of theapparatus are such that the drop height is small enough to minimize therisk of damaging the semiconductor devices.

The apparatus 300 may further comprise a manual bar code scannerconfigured to scan a bar code of the carrier 4 and the foil bag 305. Thebar codes help to retrace the content of individual transportcontainers.

Although embodiments and advantages have been described in detail, itshould be understood that various changes, substitutions and alterationscan be made herein without departing from the spirit and scope of theinvention as defined by the appended claims.

Moreover, the scope of the present application is not intended to belimited to the particular embodiments of the method and apparatusdescribed in the specification. As one of ordinary skill in the art willreadily appreciate from the disclosure of the embodiments, method andapparatus, presently existing or later to be developed, that performsubstantially the same function or achieve substantially the same resultas the corresponding embodiments described herein may be utilizedaccording to the described embodiments. Accordingly, the appended claimsare intended to include within their scope such methods and apparatus.

While embodiments have been illustrated and described with respect toone or more implementations, alterations and/or modifications may bemade to the illustrated examples without departing from the spirit andscope of the appended claims. In particular regard to the variousfunctions performed by the above described components or structures(assemblies, devices, circuits, systems, etc.), the terms (including areference to a “means”) used to describe such components are intended tocorrespond, unless otherwise indicated, to any component or structurewhich performs the specified function of the described component (e.g.,that is functionally equivalent), even though not structurallyequivalent to the disclosed structure which performs the function in theherein illustrated exemplary implementations.

What is claimed is:
 1. A method for separating semiconductor devicesfrom a wafer, the method comprising: arranging semiconductor devices ona carrier, and simultaneously removing most or all of the semiconductordevices from the carrier using a heat application step, and at least onepulse of gas from a gas jet after the heat application step.
 2. Themethod of claim 1, further comprising providing an adjustable adhesionforce between the carrier and the semiconductor devices.
 3. The methodof claim 1, wherein the carrier comprises an adhesion-adjustable foil.4. The method of claim 3, wherein the adhesion-adjustable foil comprisesa thermo-release foil.
 5. The method of claim 1, wherein after releasefrom the carrier the semiconductor devices are transferred to anapparatus for sorting and aligning the semiconductor devices.
 6. Themethod of claim 1, wherein the semiconductor devices are plasticpackages.
 7. The method of claim 1, wherein the semiconductor devicesadhere to the carrier such that an active side of the semiconductordevices faces the carrier.
 8. The method of claim 1, wherein thesemiconductor devices are singulated prior to removing the semiconductordevices from the carrier.
 9. A method of producing semiconductordevices, the method comprising: arranging semiconductor devices on athermo-release foil; providing an adjustable adhesive force between thethermo-release foil and the semiconductor devices; applying at least onemechanical or acoustical impulse to the thermo-release foil which causesdetachment of at least some semiconductor devices from thethermo-release foil; and regulating the adhesive force between thethermo-release foil and the semiconductor devices by heating thethermo-release foil from a side where no semiconductor devices areattached; wherein the at least one impulse is created using at least oneair stream that is applied to a side of the adhesive foil where nosemiconductor devices are attached.
 10. The method of claim 9, whereinheating is performed using one of an infrared lamp, an oven, and a hotair dryer.
 11. An apparatus for the separation of semiconductor devicesfrom an adhesive foil, comprising: a supporting unit for supporting anadhesive foil, the adhesive foil having semiconductor devices adheredthereto on a first side and having an opposing second side free ofsemiconductor devices, and a heating system and an impulse generator,wherein: the heating system to apply heat to the adhesive foil from thesecond side simultaneously opposite all semiconductor devices adhered tothe first side, and the impulse generator to apply at least one pulse ofgas from a gas jet to the second side of the adhesive foilsimultaneously opposite all semiconductor devices adhered to the firstside.
 12. The apparatus of claim 11, further comprising: a mechanicalseparating unit configured to isolate predetermined semiconductordevices.
 13. The apparatus of claim 12, further comprising: a vibrationunit for vibrating the mechanical separating unit.
 14. The apparatus ofclaim 11, further comprising: a reservoir to receive the semiconductordevices after mechanically separating a predetermined semiconductordevices.
 15. The apparatus of claim 11, wherein the heating system andthe impulse generator are arranged within a cohesive module.